Thursday, August 24, 2017

Safety Critical Areas and Safety Critical Functions

In the production of aircraft parts there are parts and systems that are more important to maintain safety than other systems. Not all systems are equal important for the safe operations of an aircraft and these systems are the safety critical areas. Within these systems there are parts with identified functions that have a higher probability of causing a catastrophic outcome of the flight when malfunctioning.

Safety critical tools are vital to safety performance.
As with parts, within flight operations there are operational systems that are safety critical areas for the safety of a flight. Within these areas there are safety critical functions, or processes, that are safety critical to operations. Not all flight operational systems and processes are critical for the safety of a flight. In an SMS world, the tasks become to identify what are the vital few safety critical areas and functions of flight operations and what are the trivial many areas and functions.

It is commonly said, accepted in the aviation industry and demanded by the public that regulatory requirements are the minimum requirements for the safe operations of an aircraft. Nothing is farther from the facts than this statement since regulatory compliant pilots, aircraft and operators have since the first flight of 1903 experienced catastrophic accidents. If regulatory requirements were minim safety requirements there would be no accidents. Regulations are the risk level accepted by a Governing State for a Certificate to be issued to an operator with an expectation that catastrophe accidents could happen within undefined intervals. The intent, or design of regulations is not to set up for failure, or accidents, but regulatory compliance itself does not prevent accidents. Regulatory compliance is the authority for an Operator to provide a service to the flying public. However, there is one exemption to this: Where a Safety Management System is regulatory required the accountability and responsibility for safety is placed on the Operator. For an Operator, it is not acceptable to operate within a culture that accepts a catastrophic accident at any intervals, or operate with a risk level that accepts accidents. “We don’t manage Risks; we lead personnel, manage equipment and validate operational design for improved performance above the safety risk level bar.”

The flying public does not accept that safety critical is identified at the onset.
Safety critical areas and safety critical functions are the safety risk level bar which must be exceeded for continuous safety improvements in operations. The demanding task becomes to define and decide on what systems are safety critical, what processes are safety critical functions and what is not safety critical in operations. The purpose of defining safety crucial areas and functions is to operate an SMS that is compatible with safety and not a bureaucratic system for the purpose of supporting the SMS design. If what we do does not promote safety or improve safety, we are just spinning our wheels and reactive processes becomes the determining factor for safety improvements. A proactive safety management system is to define safety critical areas and functions.

Safety Critical Factors in aviation are Human Factors, Organizational Factors, Supervision Factors and Environmental Factors. Derived from these Safety Critical Factors are SMS processes as tools for continuous safety improvements. Data collected are analyzed in a Statistical Process Control software, SPC for Excel ( and analyzed in Pareto charts, Attribute control charts or Variable control charts. If an Operator has not collected enough data to analyze processes it is possible to “borrow” data and analyze as applicable to the Operator. These tools are for each Operator to define within their Enterprise what are Safety Critical Areas and Safety Critical Functions and analyze data collected for applications to implement safety changes. Unless SMS is transformed into action it is nothing else but a check-box tool in support of defined processes.